Dust-proof carton



July 16, 1963 R. v. BURT ETAL 3,097,783

DUST-PROOF CARTON Filed March 6, 1961 1 u l 4.5 l l JNVENToR. RoERTEV. Bum,

BY Vmsu. .GExAND FIG' 2' NoRMAN J. FRANZ,

t Awonuevaadw q ma.

United States Patent O Filed Mar. 6, 1961, Ser. No. 93,490 2 Claims. (Cl. 229-37) This invention relates to improved cartons, and more particularly, to econornioal sealed-end cartons especially adapted for packing powdery or dusty materials.

Fowdery or dusty materials are normally packaged in tubular knock-down cartons having front, rear, .and end Walls, :all of which carry sealing aps. The flaps .on the front and rear walls are usually of full size, i.e. of a size to extend 'across the erected canton, while the flaps on the end walls are of a width such that they lie in the same plane in the closed carton. As is well known, however, such cartons lare subject to sifting or dusting particularly at the corners and particularly yat that seal Which is formed last. If it were possible to seal both ends of the carton over mandrels which would hold the llaps together until the adhesive had set, a better result could be obtained. The art has provided various means for amel-iorating the sifting tendency such las the so-called Van Buren e-ars, which are auticuliated to the ends of the innermost full size ilap, -and are bent over land secured to the end walls of the carton.

Dusting or sifting usually occurs fat the corners of the carton. It has hitherto been suggested that the condition might be corrected in part lat least by the use of extra quantities of adhesive at the corners. However, this expedient entails the `disadvantage that extra adhesive may exude from the corners upon the application of the sealing pressure and impair the :appearance of the structure. It has also been suggested that cartons might be made with short flaps on the body walls which flaps are mitered at the corners, the carton being then closed by a. sheet of paperboard which overlaps and is adhered to the flaps. Such structures, however, present the same problem as is outlined above.

It is an object of this invention to provide an improved carton which will retain a dusty or powdery material without leakage under ordinary conditions of packing, storage, and shipment.

It is yal1 lobject of the invention lto provide a dust-tight carton suitable for use as a retail package for soap granules, detergent powders, powdered soap, soap flakes, and the like.

lit is a further object to provide a carton having the rigidity and strength required to resist the stresses of packing, stacking, and handling, and in which the dusting problem has been reduced to a minimum, While employing the least possible quantity of paperboard.

An additional object is to provide `a carton having a minimum area of non-essential overlap of aps by employing thermoplastic adhesives which become an integral part of the package.

It is an object of the invention to provide a carton of such `character that equally effective seals may be formed at each end and without the use of an interior mandrel.

It is an object of the invention to provide a carton in which corner siftage is prevented or minimized without the exudation of such quantities of adhesive as would impair the lappearance of the carton las a retail package.

These and other objects of the invention, which will be set forth hereinafter or will be apparent .to one skilled in the art upon reading these specications, are accomplished by that structure |and arrangement of parts of which an exemplary embodiment will now be described.

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Reference is made to the raccompanyg drawings wherein:

FIG. .1 is la plan View of a cut and scored carton blank from which the structure of this invention may be made. FIG. 2 is la perspective view of the carton after it has been squared up and closed upon one end.

FIG. 3 .is a top plan view of the carton at the time of the 'application of the adhesive in forming the end seal.

FIG. 4 is a partial perspective view showing the carton sealedV at the top.

In FIG. 1 solid lines represent the edges of the carton blank or lines of cut While dotted lines represent lines of score. In the exemplary embodiment, the body of the canton comprises a back wall 1, a side wall 2, a front wall 3, a side wall 4, and a glue llap 5 articulated together by the usual score lines in the order named. As shown, the back Wall 1 earnies end ilaps `6 land 8 of full size, i.e. dimensioned to cover the entire cross-section of the carton when the `carton is in squared-up condition. While both of these flaps have been shown as articulated to the back wall, one or both of them could be articulated to the front wall if desired. The remaining body walls are provided with narrow flaps 10, 11 and 12, on one end, and 1'3, d4

and 15 on the other end. These narnow ilaps in -a carton of a -size to hold 20 oz. of detergent, by way of example, may be 1A in. in width. For larger size cartons, they may be made somewhat w-ider. I-t will be evident, however, from FIG. 1 that the narrowness of the short flaps on three of the body Walls `of the carton is capable of effecting a substantial economy in board since it facilitates the nesting lof lthe carton blanks on the sheet of paperboard.

FIG. l also shows that the short llaps 10 and 15 on the side wall 2 are cut yat a 90 angle adjacent the large aps 6 and `8 but beveled on their opposite ends. The flaps 11 and 14 on the front Wall are beveled on both ends. rlhe tlaps 12 and |13 on the side wall 4 are beveled adjacent the front wall, but cut at a 90 iangle yadjacent the glue llap 5.

The carton blank of FIG. 1 may be tubed on the ordinary oamton folding Iand gluing machines by bending over the side wall 4 and the back wall 1 and adhering the glue flap 5 either to the inside or outside of the backwall, as is Well known in the art. This may be done with Water base adhesive vor hot melt adhesive as desired.

In FIG. 2 the tubular carton is shown in erected form and closed on one end. It is immaterial for purposes of the invention which end is closed first; but it will be noted that the short flaps 10, 11 and 12 are shown in partially bent-over condition so that upon the application of a suitable adhesive, the large end flap `6 may be brought over and adhered to them. Devices on carton erecting, lilling and closing machines for bending over end flap structures are well known in the art and need not here be described. However, it may be noted that the aps 10, 11 and 12 lie in the same plane and, by reason of their narrowness and the natural spring of the board, tend to maintain full contact with the flap `6 when it is bent over and held against them under pressure. It will be understood that at the time of the sealing of either end of the carton, it will be held in the machine by a conventional rack or cage which will prevent skew-ing.

However, the bare adhesive union of the ap 6 to the llaps 10, 11 and 12 is not enough to secure a sift-proof condition in the structure. The objects of this invention are attained through the concurrent use of a rapidly setting hot melt or thermoplastic adhesive, the use of extra quantities of adhesive at the corners of the structure, and the provision of means which will permit sift-proof sealing by the localization of excess quantities of adhesive at corner portions of the structure without danger of such exudation as would impair the appearance of the carto-n. Because of the above-mentioned natural spring of the narrow flaps the use of conventional adhesives is precluded. Thermoplastic adhesives are required to effect the seal quickly in the typical high speed filling operation to prevent spring back from separating the adhered surfaces.

Various thermoplastic or hot melt adhesives are available, but the preferred adhesives for use in this invention are those which, at room temperatures, are solid but fiexible, gradually softening to a fluid stage or a condition soft enough for application at a temperature of about 200 to 400 F. The adhesives, furthermore, should be resistant to water, fats, oils, weak alkalis and acids, and should be non-brittle and stronger than paperboard from 20 to +120 F. Such adhesives are made from or are constituted of a mixture of two or more materials chosen from a class consisting of vegetable starches, polyethylenes, terpene resins, vegetable or mineral waxes, and related compounds. An exemplary suitable material is sold by United Shoe Machinery Company under the trade name Thermo Grip #407 Adhesive.

It is possible to apply the adhesive to the large fiap 6 alone or to the narrow flaps 10, 11 and 12 alone, or to both. It has been found, however, that excellent results are obtained by applying the adhesive to the large flap `6 in a pattern indicated in FIG. 3 at 16, this application comprising a line of the adhesive extending peripherally along the three free sides of the flap near the edges thereof with extra quantities of adhesive at the points marked 17, 18, 19 and 20.

The adhesive should preferably be applied in a quantity sufficient to provide a stripe about 1A" in width and 0.005l thickness. Sufficient excess adhesive will preferably be applied to yield a drop approximately 2/16 in diameter by 0.015" in thickness at the points marked 17 and 18. If quantities greater than the indicated preferred amounts are employed in the formation of this closure it can readily be seen that it will be desirable to inset the adhesive stripe to minimize exudation of surplus adhesive.

Since the application of adhesive is non-rectilinear, a timed glue wheel will be employed, as will be readily understood by the skilled worker in the art. The application of excess quantities at the points marked 17 and 18 is easily accomplished in a single operation by providing the printing surfaces of the glue wheel with indentations at the corresponding points. An excess at the points marked 19 and 20 is readily affected by running the glue wheel surface slightly beyond flap 6 and onto the adjacent ends of fiaps 10 and 12 so that on closure a double thickness of adhesive is present at these corners.

The adhesive is applied preferably within a temperature range of about 275 F. to 450 F. and the flaps are closed on each other as soon as possible after the application of the adhesive. Since the adhesive is a hot melt, it sets upon cooling, the setting time being generally less than about one second. Artificial cooling is not required, al- Vthough it may be practiced if desired. Needless to say, the seals should be completed and the adhesive adequtely set before the cartons are turned through an angle of 90 as is usual in carton filling and closing machines. Since the fiaps 10, 11 and 12 are quite narrow, the filling of the carton may occur either before or after the turning over of these fiaps.

As has been indicated above, the prevention or minimizing of siftage in this invention is accomplished by the use of what may be termed excess adhesive materials at least at the front two corners of the carton; but the objects of the invention will not be adequately attained unless the excess adhesive is largely located between the approaching edges of the flaps. In order to accomplish this, the beveling of the corner portions of the flaps is not done at an angle of 45 but at a lesser angle which will be substantially between 42 and 44 and is preferably about 43. This means that the meeting edges of the narrow liaps 10, 11 and 12 do not abut each other tightly. Upon the application of the adhesive as above described and the immediate closure of the full size flap 6, the narrow flaps 10, 11 and 12 will not lie at a right angle to the respective front and side body walls to which they are attached, but will be sprung upwardly by at least a few degrees. As a consequence, the narrow fiaps are displaced as the full size fiap 6 is bent over against them, so that during the closure of the carton there is relative movement of the narrow fiaps and the full size fiap. During this movement there is not only a tendency to spread the adhesive but the squared corners of the flaps 10 and 12 engage an intermediate portion of the adhesive on the flap `6 and as the closure is completed, they tend to ydisplace the adhesive so that it will lie between the squared ends of the narrow flaps and adjacent portions of the rear wall of the carton. In a somewhat similar way the beveled edges of the flaps adjacent the front corners of the carton engage the excess of adhesive at the points 17 and 18 exerting a packing and displacing action thereon so that the excess is forced to fill up the spaces between the beveled ends of the narrow fiaps. It will be noted that as a consequence of these actions, the bulk of excess adhesive tends to lie within the carton rather than to exude to the outside.

Modifications may be made in the invention without departing from the spirit thereof. The invention having been described in an exemplary embodiment, what is claimed and is desired to be secured by Letters Paten-t is:

l. A seal-end dust-proof rectangular carton having oppositely disposed front and back walls, two oppositely disposed side walls, and end closures comprising narrow end fiaps extending inwardly from the front and side walls in substantially the same plane, the adjacent ends of the `said narrow end flaps being lmitered to `an angle of between about 42 and 44 with respect to [their line of articulation, the other end of the narrow end flaps extending from the side walls being squared at an angle of about with respect to their line of articulation, broad end fiaps extending inwardly from both ends of the back wall Iand being approximately equal in size to the cross-section of the said carton, said broad end flaps overlapping the said narrow end flaps 'and being 'bonded thereto with a thermoplastic adhesive, said adhesive being solid but fiexi- `ble at room temperature and gradually softening to a fluid state above 200 F., an excess of the said adhesive lying between the said adjacent mtered end-s of the narrow end flaps and for-ming an integral part of the said carton, and a `double thickness of adhesive interposed between the square ends of the narrow flaps extending from the side walls and the superposed portion of the broad end fiaps whereby a carton Iwith dustproof corners is formed.

2. A seal-end dust-proof rectangular carton having oppositely disposed front and 'back walls, two oppositely disposed side walls, and end closures comprising narrow end flaps extending inwardly from the -front and side walls, said narrow end fiaps lying in substantially `the same plane, the adjacent ends `of the narrow end flaps being mitered to an angle of between about 42 and 44 with respect to their line of articulation, the other end of the narrow end fiaps extending from the `side walls being squared at ian angle of about 90 with respect to their line of articulation, full size end flaps extending inwardly from `both ends of the back wall and being equal in size to the entire cross-section of the said carton when the latter is in squared-up condition, said full size end flaps overlapping the said narrow lend flaps and 'being bonded thereto with a hot `melt thermoplastic adhesive, said adhesive being solid but flexible at room temperature and gradually softening to a fluid state above 200 F., said adhesive being applied within the temperature range of about 275 F. to 450 F. and in a quantity sufficient to provide a stripe about 1A in width and 0.005" in thickness running peripherally along the three free sides yof the full size end flaps `and extending to the squared ends of the nai-now aps varticulated from the side wall-s, an excess of adhesive `suiicient to yield a drop about 1%6 in ldia-meter by 0.015" in thickness being applied at the `corners `of the full size end flaps which overlie the adjacent miitered ends of the narrow end fiaps, whereby ka double thickness of adhesive is formed between the squane `ends :of the narrow end flaps extending from the side walls land Ithe supenposed portion of the full size end rap, 'the excess o-f adhesive at the corners `of the `ful-1 size end flaps filling up the space between the adjoining mitered end aps to form a carton with dustpnoof corners.

References Cited in the le of this patent UNITED STATES PATENTS FOREIGN PATENTS Great Brit-ain Oct. 12, 1910 

1. A SEAL-END DUST-PROOF RECTANGULAR CARTON HAVING OPPOSITELY DISPOSED FRONT AND BACK WALLS, TWO OPPOSITELY DISPOSED SIDE WALLS, AND END CLOSURES COMPRISING NARROW END FLAPS EXTENDING INWARDLY FROM THE FRONT AND SIDE WALLS IN SUBSTANTIALLY THE SAME PLANE, THE ADJACENT ENDS OF THE SAID NARROW END FLAPS BEING MITERED TO AN ANGLE OF BETWEEN ABOUT 42* AND 44* WITH RESPECT TO THEIR LINE OF ARTICULATION, THE OTHER END OF THE NARROW END FLAPS EXTENDING FROM THE SIDE WALLS BEING SQUARED AT AN ANGLE OF ABOUT 90* WITH RESPECT TO THEIR LINE OF ARTICULATION, BROAD END FLAPS EXTENDING INWARDLY FROM BOTH ENDS OF THE BACK WALL AND BEING APPROXIMATELY EQUAL IN SIZE TO THE CROSS-SECTION OF THE SAID CARTON, SAID BROAD END FLAPS OVERLAPPING THE SAID NARROW END FLAPS AND BEING BONDED THERETO WITH A THERMOPLASTIC ADHESIVE, SAID ADHESIVE BEING SOLID BUT FLEXIBLE AT ROOM TEMPERATURE AND GARDUALLY SOFTENING TO A FLUID STATE ABOVE 200* F., AN EXCESS OF THE SAID ADHESIVE LYING BETWEEN THE SAID ADJACENT MITERED ENDS OF THE NARROW END FLAPS AND FORMING AN INTEGRAL PART OF THE SAID CARTON, AND A DOUBLE THICKNESS OF ADHESIVE INTERPOSED BETWEEN THE WQUARE ENDS OF THE NARROW FLAPS EXTENDING FROM THE SIDE WALLS AND THE SUPERPOSED PORTION OF THE BROAD END FLAPS WHEREBY A CARTON WITH DUSTPROOF CORNERS IS FORMED. 